Fish cluster at an ice hole, covered with thin pieces of ice, struggling for air in a pond in a park in St. Petersburg, Russia. As the long Russian winter drags on, fish in the ponds of St. Petersburg become increasingly desperate for oxygen, clustering in vast, thrashing masses at shrinking holes in the ice. Not only does ice block oxygen that could be diffused into the water from the air, but it also impedes sunlight from reaching oxygen-generating plants and algae in the water.

A flight data recorder (FDR) (also ADR, for accident data recorder) is an electronic device employed to record any instructions sent to any between electronic systems on an aircraft. It is a device used to record specific aircraft performance parameters. Another kind of flight recorder is the cockpit voice recorder (CVR), which records conversation in the cockpit, radio communications between the cockpit crew and others (including conversation with air traffic control personnel), as well as ambient sounds. In some cases, both functions have been combined into a single unit.